CHEMICAI, SELECTION" OF MOTHERS. 75 



The sample was rasped and its juice extracted by 

 twisting the pulp, held in a piece of cloth, between the 

 fingers. The density of the juice obtained was deter- 

 mined by a hydrometer (or by the displacement 

 method, which consisted in weighing a silver lingot in 

 the juice, density being then calculated), the tempera- 

 ture of the liquid being kept at 15 degrees C.;herecom- 

 mended that beets having a density of 1.050 should not 

 be used for mothers ; special tables were arranged with 

 corrections, etc. These underwent several changes, 

 until, finally, it was suggested to submit the sample of 

 beet to a strong pressure and polarize the juice 

 obtained. But to this many objections could be 

 found, for the pressed beet does not give juice of the 

 same composition as when rasped. By all these 

 methods it was necessary to make certain calculations, 

 in order to compare the juice examined with 100 grams 

 of beet. 



It was soon pointed out that the percentage of 

 foreign substances contained in beet juice decreases as 

 the specific gravity increases. While the methods of 

 selection based upon the density of juice were not gen- 

 erally adopted at the time, they have many advocates, 

 even at the present day. Herles, for example, has a 

 special apparatus for mother selection; it consists in 

 using a very small -portion of the beet, and only 5 c. c. 

 of the juice, its density being at once deter- 

 mined. It is maintained that this density gives a 

 far better idea of the sugar percentage of the beet than 

 the polarization of juice from a very small sample. By 

 this apparatus, 1200 analyses may be made in 24 hours, 

 and it has met with some success. The first hints as 

 to the possibility of ameliorating the quality of beets 

 were given by the increase in specific gravity of juice 

 from generation to generation. From the third gen- 

 eration of selected beets, the juice had a specific gravity 

 of 1.807, which corresponded to 21 per cent, sugar. 



